Turn off the water supply and flush to lower the water level
Pour white vinegar into the toilet bowl, focusing on stained areas
Let the vinegar sit for several hours or overnight
Scrub the stains with a toilet brush
Use baking soda and vinegar together for tougher buildup
Apply a pumice stone gently to mineral deposits, keeping it wet
Use a commercial limescale or hard water stain remover
Repeat the treatment if stains remain
Turn the water back on and flush after cleaning
Wipe and clean the toilet regularly to prevent future stains